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<title>An Instrument Gauge</title>
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          <h1 class="mb-0 p-1 ">GoJS</h1>
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    <!-- Start of GoJS sample code -->
    
    <script src="../release/go.js"></script>
    <div class="p-4 w-full">
    <script id="code">
    function init() {
      var $ = go.GraphObject.make;

      myDiagram = $(go.Diagram, "myDiagramDiv");

      myDiagram.nodeTemplate =
        $(go.Node, "Auto",
          $(go.Shape, "Circle",
            { stroke: "orange", strokeWidth: 5, spot1: go.Spot.TopLeft, spot2: go.Spot.BottomRight },
            new go.Binding("stroke", "color")),
          $(go.Panel, "Spot",
            $(go.Panel, "Graduated",
              {
                name: "SCALE", margin: 14,
                graduatedTickUnit: 2.5,  // tick marks at each multiple of 2.5
                graduatedMax: 100,  // this is actually the default value
                stretch: go.GraphObject.None  // needed to avoid unnecessary re-measuring!!!
              },
              new go.Binding("graduatedMax", "max"),  // controls the range of the gauge
              // the main path of the graduated panel, an arc starting at 135 degrees and sweeping for 270 degrees
              $(go.Shape, { name: "SHAPE", geometryString: "M-70.7 70.7 B135 270 0 0 100 100 M0 100", stroke: "white", strokeWidth: 4 }),
              // three differently sized tick marks
              $(go.Shape, { geometryString: "M0 0 V10", stroke: "white", strokeWidth: 1.5 }),
              $(go.Shape, { geometryString: "M0 0 V12", stroke: "white", strokeWidth: 2.5, interval: 2 }),
              $(go.Shape, { geometryString: "M0 0 V15", stroke: "white", strokeWidth: 3.5, interval: 4 }),
              $(go.TextBlock,
                { // each tick label
                  interval: 4,
                  alignmentFocus: go.Spot.Center,
                  font: "bold italic 14pt sans-serif", stroke: "white",
                  segmentOffset: new go.Point(0, 30)
                })
            ),
            $(go.TextBlock,
              { alignment: new go.Spot(0.5, 0.9), stroke: "orange", font: "bold italic 14pt sans-serif" },
              new go.Binding("text", "key"),
              new go.Binding("stroke", "color")),
            $(go.Shape, { fill: "red", strokeWidth: 0, geometryString: "F1 M-6 0 L0 -6 100 0 0 6z x M-100 0" },
              new go.Binding("angle", "value", convertValueToAngle)),
            $(go.Shape, "Circle", { width: 2, height: 2, fill: "#444" })
          )
        );

      // this determines the angle of the needle, based on the data.value argument
      function convertValueToAngle(v, shape) {
        var scale = shape.part.findObject("SCALE");
        var p = scale.graduatedPointForValue(v);
        var shape = shape.part.findObject("SHAPE");
        var c = shape.actualBounds.center;
        return c.directionPoint(p);
      }

      myDiagram.model = new go.GraphLinksModel([
          { key: "Alpha", value: 35 },
          { key: "Beta", color: "green", max: 140, value: 70 }
        ], [
          { from: "Alpha", to: "Beta" }
        ]);

      loop();
    }

    // change each gauge's value several times a second
    function loop() {
      setTimeout(function() {
        myDiagram.startTransaction();
        myDiagram.nodes.each(function(node) {
          var scale = node.findObject("SCALE");
          if (scale === null || scale.type !== go.Panel.Graduated) return;
          // keep the new value within the range of the graduated panel
          var min = scale.graduatedMin;
          var max = scale.graduatedMax;
          var v = node.data.value;
          if (v === undefined) v = Math.floor((max - min) / 2);  // default to middle value
          if (v < min) v++;
          else if (v > max) v--;
          else v += (Math.random() < 0.5) ? -0.5 : 0.5;  // random walk
          myDiagram.model.setDataProperty(node.data, "value", v);
        });
        myDiagram.commitTransaction("modified Graduated Panel");
        loop();
      }, 1000 / 6);
    }
    window.addEventListener('DOMContentLoaded', init);
  </script>

  <div id="sample">
    <div id="myDiagramDiv" style="border: solid 1px black; width:100%; height:350px"></div>
    <p>
      This makes use of a <a href="../intro/graduatedPanels.html">"Graduated"</a> <a>Panel</a>,
      which holds the main path of the scale, a Shape whose <a>Shape.geometry</a> is a circular arc.
      In addition that Graduated Panel holds three different Shapes acting as templates for tick marks and
      a TextBlock acting as a template for tick labels.
    </p>
    <p>
      In a Spot Panel with the Graduated Panel scale are an italic TextBlock showing the node identifier and a red elongated diamond "needle" Shape.
      The needle's angle is determined by <code>convertValueToAngle</code>, which finds the point on the Graduated Panel's
      main path element corresponding to <code>data.value</code> and computes the angle from the center to that point.
      The data value is updated several times per second.
      A circle Shape surrounds the Spot Panel.
    </p>
  </div>
    </div>
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